1. Field of the Invention
The present invention relates to a wind power generation system that uses natural wind to cool an internal device.
2. Description of the Related Art
In a typical wind power generation system, a rotor, which is rotated by blades, is supported through a main shaft by a nacelle located at the top of a tower. The nacelle often houses a generator, which is rotated by the rotation of the main shaft of the blades. To obtain a suitable rotational speed of the generator, a gearbox is located between the rotor and the generator to increase the rotational speed of the generator in some cases. Electric energy generated by the generator is converted by a power converter and a transformer to electric power that can be supplied to a utility grid.
Devices housed in the wind power generation system, such as the generator, the gearbox, the power converter, and the transformer, generate heat, which is the loss from the devices. Hence, there is a demand for a cooling system that enables such generated heat to dissipate, so that the devices can be operated at appropriate temperatures. Systems using a heat dissipator (radiator) and/or a fan are often used to dissipate the heat eventually into water or atmosphere outside the wind power generation system. A cooling system described in JP 2012-233481 A includes no fan, which is a moving part. This document describes an arrangement with a cooling device (a radiator) provided on the top of a nacelle for cooling by natural wind in order to remove the heat of a wind power generation system into the ambient air. An arrangement described in JP 2012-072684 A cools a transformer and a generator located in a nacelle with air introduced into the nacelle by natural wind. An example of an upwind type windmill is described in JP 2009-185641 A, which includes a nacelle having a vent hole in its upwind wall and a heat exchanger is provided at this vent hole.